<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <script src="../../react18/react.development.js"></script>
    <script src="../../react18/react-dom.development.js"></script>
    <script src="../../react18/babel.min.js"></script>
  </head>
  <body>
    <div id="app"></div>
    <script type="text/babel">
      class Child extends React.Component {
        state = {
          b: 2,
        };
        /* 
             static getDerivedStateFromProps
                通过props得到第一个派生的state
                第一个参数是props 第二个参数是state
                函数返回的对象，最早会通过setState的方式合并到道歉组件的state中
        */
        static getDerivedStateFromProps(props, state) {
          const { a } = props;
          return { myA: a };
        }

        render() {
          return (
            <div>
              <h2>Child组件</h2>
            </div>
          );
        }
      }

      class App extends React.Component {
        constructor() {
          super();
          console.log("****constructor****");
        }
        render() {
          console.log("****render****");
          return (
            <div>
              <Child a="1" />
              <h2>这里是App组件</h2>
            </div>
          );
        }
        componentDidMount() {
          console.log("****componentDidMount****");
        }
      }
      ReactDOM.createRoot(document.getElementById("app")).render(<App />);
    </script>
  </body>
</html>
